Apparatus for feeding bagasse



" June 18, 1957 A. c. wElGEl. ErAL 2,796,198

APPARATUS FOR FEEDING BAGASSE original Filed Aug. 2o, 1947 5 sheets-sheet 1 INVENTORS Albrt C. Weigel BY Harold G. Meissner @5.62E- ATTOR Y A. C. WElGEL ETAL.

APPARATUS FOR FEEDING BAGASSE original Filed Aug. 2o, 1947 June 18, 1957 2,796,198

5 Sheets-Sheet 2 Fig. 2. A v

INVENTORS Alb rtA G. Weigel Hor G. Meissner l 'BY' AT1-ORN Y June 18, 1957 A. c. WEIGEL ETAL APPARATUS Foa FEEDING BAGASSE 5 Sheets-Sheet 3 Original Filed Aug., 20. 1947 INVENTORS Albert C. Wigel Harold G. Melssner Fig. 4.

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June 18, 1957 A. c. wElGEl. ET Al. 2,796,198

y l APPARATUS FOR FEEDING BAGASSE Original Filed Aug. 20, 1947 5 Sheets-Sheet 4 v v"4 INVENTORs Flg 5 Alben c. Weigel.

' Harold G. Meissner v Y Kfm ATTO RN June 18, 1957 A. c. wElGEL ETAL APPARATUS FoR FEEDING BAGAssE original Filed Aug. 2o, 1947 5 Sheets-Sheet 5 INVENTORS Albert C. Weigel BY Harold G. Meissner E7 ATTOR Y United States Patent O APPARATUS FoR FEEDING BAGASSE Albert C. Weigel, Bradenton, Fla., and Harold G. Meissner, Mount Vernon, N.- Y., assignors to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Continuation of application Serial No. 769,560, August 20, 1947. This application May 13, 1954, Serial No. 429,661

7 Claims. (Cl. 222-80) This application is a continuation of co-pending paren U. VS. application Serial No. 769,560, tiled August 20, 1947, now abandoned, in the names of Albert C. Weigel and Harold G. Meissner under title of Art of Burning Bagasse.

The invention hereof relates to the feeding and burning of bagasse and other cellulose fuels of similar character and it has special reference to a new technique and to improved apparatus for successfully feeding such bagasse-type fuels to and for burning those fuels in furnaces for the generation of steam and for other purposes.

Broadly stated, the object of this invention is to burn bagasse-type fuels more conveniently and more efficiently than has been possible heretofore and to enable such burning to proceed continuously without the prior necessity of periodic furnace shut down.

A more specific object is to simplify the constluction, lower the cost and improve the performance of furnace apparatus wherein cellulose fuels of the bagasse type can effectively be burned.

Another object is to accomplish satisfactory burning of bagasse-type fuels on furnace grates (both stationary and traveling) when spreader stokers are used to -feed the fuel to those grates.

A further object is to enable the so used spreader Stoker to distribute the bagasse fuel over the .grate surface with such controlled uniformity that even and complete burning will be assured and that fire blanketing will not occur (as in spots or otherwise) anywhere on the grate.

A still further object is to provide improved feeder apparatus capable of supplying the bagasse fuel to the spreader stoker impeller at a closely controlled uniform rate which may be accurately adjusted through a wide range of fuel-feed speeds.

An additional object is to coordinate the several elements of the complete furnace-stoker-feeder system in a way uniquely matched with the special characteristics and burning requirements of bagasse-type fuels.

Other objects and advantages will become apparent from the following description of an illustrative embodiment of the invention when taken in conjunction with the accompanying drawings wherein Fig. l is a longitudinal section (as on line 1--1 of Fig. 2) through a steam generating furnace equipped with the improved spreader Stoker apparatus and organized to practice the new bagasse-burning technique herein disclosed;

Fig. la shows how the stationary dump-type grate of Fig. 1 may be replaced by a traveling grate of the continuous discharge type;

Fig. l2 is a front elevation of the Fig. l furnace apparatus, as viewed from line 2 2 of Fig. 1, showing further fuel feeder, supply duct and spreader stoker details;

Fig. 3 is an enlarged section on line 3-"-3 through ICC 2. one of the spreader stokers of Fig. 2 showing the rotary distributor and other internal stoker parts;

Fig. 4 is an enlarged section on line 4 4 through the bagasse fuel feeder of Fig. 2 (and also of Fig. 5) showing the rotary drum and other internal feeder parts;

Fig. 5 is an enlarged section on line 5--5 through the rotary fuel feeder of Fig. l (and also of Fig. 4r) showing the drum-carried fuel-cutter parts and other rotary feeder details;

Fig. 6 is a side View partly in section and partly in elevation showing a belt-type of bagasse fuel feeder which may be used with the spreader stoker of Figs. 1-la 23 in place of the rotary feeder earlier represented;

Fig. 7 is a top plan showing of this belt-type feeder as viewed from line 7-7 of Fig. 6; and

Fig. 8 is a section on line 8 8 of Fig. 6 showing how the flights on the conveyor belt may be provided with serrated cutting edges.

Bagasse and prior burning practice The fuel known as bagasse comes from sugar cane. Such cane is grown in many parts of the world but most abundant production is in tropical locations such as Florida, Louisiana, Mexico, Cuba, Hawaiian Islands, Brazil, Argentina, Peru, Australia, Egypt and India. At harvest time the cane is cut in the fields, the leaves and tops removed and discarded, and the cane stalks then brought to the processing plant. Here these stalks are ground in roller mills to remove the sugar syrup. The stalk refuse from this grinding constitutes the bagasse here considered.

Syrup extracting mills range in size from the small ones grinding tons of cane in twenty-four hours to those grinding 1000 tons or 2000 tons in this period, and some are still larger. A 2000 ton mill may require as high as 100,000 to 150,000 pounds of steam per hour for operation, and the mills generally work for twenty-four hours per day, seven days per week for the grinding season. This season last until the quota is ground, which may take three to four months. A few mills throughout the world operate 365 days per year.

This operation yields tremendous quantities of cane refuse (bagasse) and the ideal form of disposition is burning to produce steam needed for running the mill as well as for other useful purposes such as refining the cane syrup and the powering of irrigation pumping. In many present-day installations supplementary fuel (such as oil) is found necessary for the steam boilers; moreover, immediate incineration burning of any substantial excess bagasse is preferable to storage in a pile or to hauling away because the bagasse takes up such extreme ly large spaces and is so diiiicult later to take out of storage. Hence there is an urgent need for expedients to increase both the efficiency and the convenience with which bagasse and other similar cellulose fuels can usefully be burned.

The named bagasse from sugar cane stalks has a structure of fibrous cellulose. Its analysis is much like wood, typically being from 40 to 50% carbon, several percent hydrogen, from 35 to 45% oxygen, and several percent of ash and other ingredients. Its water content is typically high, being from 45 to 55% as taken from the grinding mill. In this condition the cane may have a heating value of from 3500 to 6500 B. t. u. per pound. Such ground cane when freed of moisture and ash has a somewhat higher heating value of which about 8350 B. t. u. per pound is typical.

In modern plants recovering as high as 98 to 99% 4of the sugar the cane is so finely crushed and ground that it resembles wood shavings; but in other processings the K f a cane structure is less thoroughly broken up and fibres several inches in length are not uncommon. Bagasse is therefore not only wetter, but also much lighter and more bulky than coal and other conventional fuels in divided form. One Cuban grade of bagasse weighs up to only 6.25 pounds per cubic foot as it leaves the grinding mill; this .compares with about 90 pounds per cubic foot for coal When `solid and with from 45 to 50 pounds per cubic foot weight of the coal when crushed into lumps for burning on 'a furnace grate. Moreover, the bagasse fibres become so closely intermingled that pulling apart for feeding in a small and closely controlled uniform stream has heretofore been considered impossible.

These and other characteristics make bagasse a very stubborn material to deal with; and prior to the present invention burning thereof either for the useful production of steam or for direct incineration disposal has been both diliicult and unsatisfactory.

Past practice in the burning of this bagasse has been to provide a Dutch oven form of combustion chamber defined by a brickwork erected outside of the main boiler setting and communicating therewith only by a shallow throat. ln a typical arrangement (not shown) the rbagasse coming from the sugar mill or tandem is dropped directly through an opening in the oven top. It then piles up in the chamber like a haymow and burns very much like a bonfire from the outside of the pile on the chamber hearth. This hearth requires periodic cleaning (as frequently `as every eight hours) to remove accumulated ash and each cleaning occasions furnace shut down. Latter may range from a few minutes to half an hour. Moreover, dy ash and clinkers accumulating in the boiler passes of such furnaces may require removal as often as once each week when a twentysfour hour shut down is not uncommon.

In addition to interrupting continuity of steam generation the attendant cooling and reheating deteriorates the oven and furnace brick work and the boiler pressure parts thereby occasioning short life land high maintenance. Moreover, the ovens physical separation from the main boiler setting permits high thermal losses with resultant lowered efficiency of heat transfer to the boiler water. Still further, before bagassc combustion can initially be started the oven walls `and roof must first be thoroughly preheated (by burning substantial quantities of kindling) since radiant heat from those parts is depended upon to evaporate the bagasse moisture.

Such prior techniques of bagasse burning are therefore subject to serious disadvantages, all of which the present invention overcomes as will now be described.

Improved burning7 technique of this invention ln accordance with this invention bagasse in the highmoisture-content condition as taken from the syrupextracting mill is dried above and is burned partly over and partly on a grate of either the stationary or traveling type, which grate constitutes the bottom of a furnace combustion chamber that is housed within and that forms a part of the main boiler setting. This bagasse is introduced into the furnace over the named grate by a spreader Stoker mounted above the grate level. This stoker receives the `bagasse from a unique feeder at a specially controlled rate which 'assures uniform spreading over the grate surface area. Drying and partial combustion occurs during passage from the Ispreader distributor toward the grate surface through the hot gases rising therefrom; the dried unburned material then falling on the grate is thereupon completely burned thereon.

The several elements of this new furnace-stoker-feeder system are coordinated with and matched to the special characteristics .of the bagasse (bulky, wet and tenacious) in a novel way which uniquely satisfies the burning requirements thereof and which results in a far more efficient and convenient combustion of the bagasse than has been possible heretofore.

4 The illustrative boiler-furnace Referring to the drawings, the new burning facilities are illustratively disclosed as being 4applied to a steam generator shown in Figure 1 as comprising boiler tubes 10, upper and lower drums 11 and 12 interconnected :by those tubes, and furnace water Wall tubes 13 also connected into the boiler circulation system in well known manner. Feed water suitably introduced into that pressure-part system is converted (by fuel-combustion heat produced as later described) into steam which leaves the upper drum 11 by way of outlet 14 and passes to the point of use either directly or through a superheater (not shown) also within the main boiler setting. Such setting may satisfactorily include a front wall 15, roof 16, rear wall 17 and spaced side walls which complete the boiler-furnace enclosure. One such side wall 18 is shown at the right of Fig. 2; the companion side wall at the eXtreme left of the setting is not there represented.

The furnace grate is positioned in customary manner at the bottom of the steam generators combustion chamber, here shown as being surrounded by water-wall tubes 13. In Fig. l this grate is illustrated at 2f as being of a conventional dump type; in Fig. la it is shown at 22 as -being of an equally well known continuous-discharge traveling type. In the case of Fig. ls stationary grate 21, ash collecting thereon is at periodic intervals dumped into the space therebeneath by a temporary tilting (manual or other) of the individual grate bars in conventional manner. In the case of Fig. las traveling grate 22, the slow movement (by suitable driving means no-t shown) from rear to front (this grate may also be designed to travel from front to rear) causes accumulating ash to be continuously discharged from one end of the grate `as indicated by the Fig. la arrow.

The boiler furnace equipped with the stationary or dumping grate 21 of Fig. l is preferably arranged so that the total width of combustion chamber oor is divided into two or more sections indicated at A-B-C in Fig. 2 and so that the grate for each of these sections can be operated independently of the adjoining section grates. This arrangement is desirable in that following ash removal (as by dumping) from any one of the grate sections further bagasse then added thereupon will automatically rekindle itself from the burning fuel on adjoining grate sections.

In the apparatus shown hot gases produced by bagasse combustion on and above each grate 21 or 2.2 rise upwardly through the combustion chamber between front wall 15 and the chambers rear partition or bridge wall 24, pass over the top of the latter and thence downwardly through boiler tubes 10 below tube baffle 2S, thence upwardly along tubes 10 and over a second bafe 26 and then out of the boiler furnace by way of an air heater 27 (optional but here illustratively shown as of the tubular type) and an induced draft fan 28; combustion-supporting air entering heater 27 by way of inlet 30 (from a forced draft fan not shown) has its temperature raised (by heat absorbed from the furnace-leaving ue gases) to some proper value, then passes downwardly through side conduit 31 into the windbox 32 beneath grate 21 or 22, and thereafter upwardly through the grate to support the bagasse combustion; and the forced-draft air thus admitted into the wind box space below each grate may be adjusted by manipulating a damper such as shown at 33 in Fig. 1.

For installations in which steam must at times be generated even though a supply of bagasse may not be continuously available, the boiler furnace may further be provided with an auxiliary oil burner such as shown at 36 in Fig. l. Preheated forced-draft air may at proper times then be supplied from heater 27 to `that burner upon an opening of dampers 38 in the burner duct and a closure of dampers 39 in the parallel grate duct 31. Such auxiliary standby is entirely conventional and hence forms no part of the present invention.

Also indicated in the complet-'e boiler'furnace here represented are high pressure jet means for returning cinders recovered in boiler and air heater hoppers 41-42 back into the combustion chamber at point 43 where any combustible `content is usefully burned. Still lfurther indicated above the furnace grate'21 (or 22) are overlire air jets 44 supplied with forced draft air by way of a duct 45 that communicates with `outlet conduit 31 leading from the inlet 30 by Way of air heater 27.

As designed for one typical bagasse-burning installation the boiler-furnace of Figs. 1 to 3 has a full-load output capacity of 60,000 pounds of steam per hour at 160 pounds per square inch pressure; an overall height from the foundation floor to the top of steam outlet 14 of approximately twenty-four feet; a front-to-rear setting depth (wall 15 to wall 1'7) of approximately twenty one feet; a side-to-side setting width (only partially represented in Fig. 2) of approximately eighteen feet; a frontto-rear length for grate 21 of nine feet; and a side-toside width for each section A-B-C etc. of grate 21 of 'four feet. The four such sections A-B etc. included in the complete furnace thus provide a total grate area of one hundred forty-four square feet.

The bagasse-introducing apparatus In accordance with this invention bagasse in the highmoisture content condition as taken from the syrupextracting mill may with outstanding success and unparalleled convenience be introduced into and efficiently burned by boiler furnaces of the just described and equivalent types. Such introduction is accomplished through the medium of: (a) one or more spreader Stoker units represented at 46 and provided as shown for each of the several furnace grate sections as best indicated by Figs. 2 and 7; (b) a bagasse supply chute or gravity spout 47 leading upwardly from each spreader unit outside of the boiler-furnace setting; (c) a bagasse feeder 48 at the top of each supply chute 47 novelly organized to drop the incoming bagasse into the chute at a closely controlled and accurately adjustable rate; and (d) conveyor mechanism 49 for delivering the bagassee from the tandem or cane crushing mill (or other point) into the top of each of the feeders 48.

Bringing bagasse from mill to furnace The bagasse to be burned in a boiler furnace such as earlier described may satisfactorily be brought thereto from the cane crushing mill or other supply source by conveyor mechanism 49 which runs in front of the furnace top as indicated by Figs. l and 2. In the representative showing of those views the conveyor is there suitably mounted about twenty feet above oor level and with its center line some ten feet from the furnace front Wall 15.

Such a positioning is typical of existing sugar mill installations in which a prior art Dutch oven (not shown but earlier described) is installed in front of the main boiler setting for reception of the bagasse (through top opening in oven) by direct dropping from the conveyor. Once so installed such a conveyor cannot readily be moved.

In the system of this invention the external Dutchoven structure is totally eliminated and replaced by the more efficient, compact and convenient spreader Stoker and special feeder apparatus now to be described.

The bagasse spreader Stoker Each of the spreader stoker units 46 may satisfactorily be mounted in the furnace front wall 15 as shown above the level of the associated grate 21 or 22 and in such position as to spread the bagasse over the entire top surface of that grate. The spreadersrotary distributor 51 is provided with the usual impeller blades spaced therearound at 90 or other suitable circumferential intervals as indicated at 52 in Fig. 3. In the construction shown each of these blades 52 is segmented lengthwise of the distributor; each segment is inclined with respect to the distributor shaft by about 30; and the blade segments in circumferentially adjacent impeller rows S2 are opposed in their directions of angular inclination as Fig. 3 further indicates. Other constructions and blade arrangements are of course useable.

'In the organization shown each distributor 51 is rotated (see direction arrow of Fig. 3) so as to overthrow feed the bagasse onto the furnace grate 21 or 22 therebeneath, as indicated by the particle-travel arrows of Figs. l and la. A satisfactory speed for such rotation when so feeding the bagasse is within the range of from 300 to 600 R. P. M. Driving of each distributor may satisfactorily be through a chain 53 (see Figs. 2 and 3) from a line shaft 54 that is driven by a motor or other suitable power source 55 and that drives adjacent spreader Stoker units 46 in parallel, as Fig. 2 indicates. This assures the same speed for all units and permits simultaneous speed adjustment thereamong.

Inoperation of each spreader stoker 46, bagasse descending by gravity through feed chute 47 is directed by baffle plate 56 (see Fig. 3) upon rotating impeller blades 52 and by them thrown inwardly into the combustion space above furnace grate 21 or 22. The blade rotating speed is adjusted to the value at which the bagasse distributes itself uniformly lengthwise of the grate surface asvFigs; 1 and la indicate; the coarser and heavier particles traveling farthest to the grate rear, the intermediate sized particles falling at intermediate locations and the smallest and lightest particles traveling the least distance inwardly and falling close to the grate front. By reason, moreover, of the staggered mounting inclinations (earlier described) of the distributors impeller segments S2, the bagasse particles are alternately thrown toward the 'right and toward the left in criss-cross fashion thereby also giving uniform distribution across the grate width and over section-to-section boundaries.

As illustratively provided for the bagasse-burning boiler furnace here described, each of the four-spreader stokers 46 (one for each grate section A-B-C etc. of Fig. 2) is mounted with the center line of its distributor 51 approximately three feet above the level of grate 21, and ea'ch of the distributors impeller blades 52 is about four inches long radially. With one grade of Cuban bagasse the desired uniform distribution over the nine-byfour foot grate section 21 is achieved when the spreader is rotated at about 450 R. P. M.

The rotary bagasse feeder of Figs. I t0 5 Successful performance of the novel bagasse burning technique of this invention depends in large measure upon 'how uniformly and with what degree of control the bagasse descends through the gravity chutes 47 into the spreader stokers 46. Should the rate of this feed be erratic the burning on and over the furnace grates will be affected adversely (as later brought out more fully); hence it is of the utmost importance that the bagasse feeders 48 function in a unique and highly reliable manner.

Each of these feeders is interposed as shown between one or more of the spreader stokers 46 and the conveyor mechanism 49 by which bagasse from the cane crushing mill or storage pile is delivered into a hopper 59 constituting the feeder top. That conveyor mechanism may satisfactorily consist of a horizontally traveling (see direction arrows in Figs. 2 and 5) chain 60 carrying spaced pushers 61 between which bagasse from the supply source lodges and by which that bagasse is continuously advanced over the open top of the feeder hopper 59 for dropping thereinto as long as room remains. The rate of such supply to the hopper top is faster than the bagasse is fed out of the hopper bottom and in this way each of the named hoppers v59 is kept continuously iilled. An outward aring of the hopper in the downward direction as shown by Figs. 2 and 5 safeguards against flat.

7 bridging of the bagasse during its descent into the feeder.

In the rotary type feeder of Figs. 1 2, 4-5 use is made of a drum 63 mounted for rotation on shaft 64 and driven lat an adjustable speed within the range of from four to twenty R. P. M. (correspondingl to a drum surface speed of from 40 to 200 feet per minute). The disclosed drive is by a constant-speed electric motor 65 through the represented chain-and-sprocket connections and a speedreduction unit 66 provided with a speed-selector lever 67. This lever provides a continuously-variable adjustment in feeder-drum speed throughout any suitable range such as of the five-to-one adjustment ratio illustratively stated; shifting to the left in Figs. 2-5 lowers tie speed of drum rotation, shifting to right raises that speed, and locking in any xed position (as by the aid of quadrant 65) holds the drum speed constantly at the value selected.

Spaced around the entire periphery of drum 63 and rigidly secured thereto for rotation therewith are flights 70 each of which preferably has the serrated cutting edge best indicated by Fig. 5. As the drum rotates (in direction shown by Fig. 4 arrow) thesc serrated ights successively pass beneath a stationary straight-edged cutter 71 mounted for adjustment up or down as conditions require.

As illustratively provided for the bagasse-burning boiler furnace earlier described, each of these rotary feeders 4S employs a drum 63 over three feet in diameter and approximately four feet long; the flights 7@ project nearly two inches out from the drum surface and are spaced approximately ve inches apart around the drurn circumference; and the feeder is mounted to give a spacing of slightly less than four feet between the top of drum 63 and the bottom of conveyor 49 running thereabove.

Such a spacing enables hopper 59 to have a substantial storage capacity for the incoming bagasse without building up above drum 63 a bagasse head sufficient to interfere with proper feeder operation. The remaining elevation difference between conveyor 49 and the spreader stoker 46 is taken up in gravity duct 47 here shown as being relatively long. Positioning of the feeder 48 (and conveyor 49) closer to the furnace front wall 15 than Fig. l indicates obviously is permissible. This will make duct 47 more closely approach the vertical.

In operation of each of these rotary feeders 4S, bagasse descending by gravity through hopper 59 rests upon the top of drum 63 and lls into the spaces between adjacent ights 70. Rotation of these flights with the drum pushes successive entrained portions of bagasse beneath stationary edge 71, completely severing each portion from the rest as the serrated flight 70 passes under that cutter edge 7l. Each so severed portion of bagasse is then further carried by the drum toward the top of chute 47 and then dropped therein.

A given and relatively unvarying quantity of bagasse is therefore released into the chute by each complete rotation of drum 63. The rate of bagasse feed to the supplied spreader stoker 46 is therefore directly proportioned to the speed of drum rotation and hence may be accurately and reliably `controlled merely by adjusting speed-change lever 67 on the feeder drive.

The belt-type feeder of Figs. 6-7-8 In Figs. 6-7-8 there is represented one manner in which `the same spaced cutter principle may be incorporated into a belt-type of bagasse feeder 48. The rigid cylinder 63 of Figs. 45 is replaced by an endless and flexible belt 74 along the outer surface of which ights 70' are spacedly mounted throughout the entire belt length. Rollers 75 support the upper run of the belt and hold it substantially A stationary `cutter 71 is mounted as shown on the belt-leaving side of feeder hopper 59 just above the top edge of the belt-carried flights 70' that pass therebeneath (see Fig. 8) as the endless belt 74 is driven by 8 apparatus 6S-66-67 corresponding to that earlier described for the rotary conveyor of Figs. 4-5.

In operation of this belt-type feeder, bagasse from conveyor 49 descending by gravity through hopper 59 rests upon the top of belt 74 and lls into the spaces between adjacent ights 70. Advancement of these tiights with the belt pushes successive entrained portions of bagasse beneath stationary edge 71', completely severing each portion from the rest as the serrated ight 70' passes under that cutter edge 71. Each so severed portion of bagasse is then further carried by the belt (to the right in Figs. 7 8) toward the top of chute 47 and then dropped therein.

A given and relatively unvarying quantity of bagasse is therefore released into the chute by each flight 70 that portional to the speed of belt travel and hence may be accurately and reliably controlled merely by adjusting speed-change lever 67 on the feeder drive.

This belt-type feeder 4S' of Figs. 6 to 8 may with advantage be used in instances where the bagasse conveyor 49 is spaced horizontally from the furnace front a distance so great (as in Figs. 6-7) that a duct 47 directly connecting the spreader stoker 46 with the rotary feeder 4S would depart too much from the vertical to `allow reliable flow by gravity of the bagasse downwardly therethrough. In practice duct inclinations from the vertical of up to 30 are always permissible; but in the range of 45 or over gravity flow of the bagasse becomes unreliable.

In both the rotary-drum `and the belt-type feeder designs best operation is realized when the hopper 59 is dimensioned to provide a bagasse head of not more than several feet above the top of drum 63 or the surface of belt 7 4. Preferably, therefore, the feeder mounting should keep these moving hopper-Hoor surfaces within about two to six feet below the bottom of conveyor A19-running thereabove; the smaller spacing being dictated by bagasse storage capacity in the feeder hopper 59, and the larger spacing by degree of compacting the bagasse between feeder flights 7i) immediately prior to passage of same beneath the stationary cutter 71.

Operation of complete bagasse-burning system which make up the system.

The bagasse, as received from the tandem or cane crushing mill, is continuously brought in by the chain advanced pushers 61 of the conveyor mechanism 49. As earlier indicated, this cane refuse is relatively tenacious and bulky; it typically contains about 50% moisture; and in the past it has proven exceedingly difficult to handle. From conveyor 49 it drops into the hopper 59 of feeder 48 and keeps that hopper continuously lled, bagasse in excess of this requirement being carried by chain 60 and pushers 61 past the hopper top. In this Way there is maintained upon the top of feeder 485 cylinder 63 (or belt 74) a depth of bagasse up to nearly four feet in thickness, a head found sufficient to provide a substantial bagasse reserve in the hopper without exerting an undesirably high pressure on the feeder parts.

As the feeder flights 70 are successively advanced beneath the stationary cutter edge 7l, each flight pushes ahead of it a segment of the bagasse which is severed from the main bagasse body in the feeder hopper 59 upon passage of the flight 7i) beneath that cutter. In this way rotation of the feeder drum 63 (or advancement of the feeder belt 74) at a given speed carries the thus severed bagasse portions successively into the top of bagasse chute 47 at a uniform rate corresponding to that particular speed. This rate of bagasse feed into chute 47 is accurately adjustable through a relatively wide range (such as the one-to-ve ratio represented by the 4 to 20 arcaica .9 drum R. P. M. earlier stated) merely by changing the setting of selector lever 67 of the feeders drive mechanism 65-66.

The bagasse thus introduced into the top of chute 47 is carried by gravity downwardly therethrough and thus drops at the chutes lower end upon the rotating impeller blades 52 of spreader-Stoker 46s distributor 4'51. Batlle plate 56 aids in directing this falling bagasse into effective engagement by the distributor bladesI 52. In this way the bagasse is supplied to those blades with the same accurately controlled and dependable uniformity with which it is released into chute 47 by the feeder 48.

As the stokers distributor S1 continuously rotates, the impeller blades 52 spread this descending bagasse into the furnace combustion chamber bythe earlier described overthrow action (indicated by the small arrows of Figs. 1, 1a and 6), the larger particles going towards the rear and the smaller falling near the front. In this way the bagasse is uniformly distributed lengthwise (i. e. from front to rear) of the grate; at the same time the staggeredly inclined mountings of the impeller blades 52 (see Fig. 3) effect uniform distribution across the width (i. e. side to side-see Fig. 2) of each of the furnace grates 21 or 22.

Thus injected into the furnace, the high moisture content 'bagasse is initially dried during its flight from the spreader distributor 51 through the hot combustion gases rising from grate 21 or 22. The smaller and finer particles which have the shortest paths of flight dry more quickly than do the coarser and Iheavier particles which follow the longest paths of flight travel. Thus it works out that fine, intermediate and coarse particles are all dried before reaching the grate surfaces with an effectiveness suicient to assure easy ignition and effective combustion.

Initial tiring of the bagasse upon first starting up the furnace is readily accomplished by the aid of conventional kindling (small quantity only sucient) and without any necessity for pre-heating the furnace walls. Once bagasse combustion is in progress, the burning proceeds rapidly and with remarkable stability. A portion of the bagasse projected into the combustion chamber burns while still in suspension over the grate, while the remainder drops upon the grate for completion of burning there. By the time such bagasse reaches the grate, it -h'as been suiciently exposed to the hot combustion gases to be thoroughly dry.

Since the spread of bagasse over the grate surface is uniform, both lengthwise and sidewise, there builds up on the 4grate surface a layer of burning bagasse which has substantially the same thin depth over the entire grate area. A typical thickness of this `burning layer of bagasse is approximately two inches, and seldom is there more than one minutes supply of bagasse fuel in the furnace. Hence, if fuel injection is shut off the bagasse on the grate will completely burn to ash in sixty seconds or less.

Moreover, an individual `bagasse particle projected into the furnace by spreader-Stoker 46 requires no more than one-half second to reach the surface of grate 21 or 22 below the spreader. During this short time interval, the particle is freed of practically yall moisture content and may even burn in :suspension before reaching the grate. I-f it -does fall to the grate without such suspension burning, it is only a matter -of less than one minute before complete combustion on the grate takes place.

A major portion of the air required for this combustion .of the bagasse passes upwardly through the bar spacings in grate Z1 or 22 from any suitable source such as windbox 32 and forced air inlet ducts 31 and 30. This underiire air also penetrates the burning bagasse layer on the grate surface and the before-explained uniformity of layer thickness is there-fore essential to satisfactory burning operation. Absence of such thickness uniformity (as the presence cf built up local areas) interferes with the desired uniform burningsince the thickened bed areas i' IO cannot receive combustion air as rapidly as 'do thinner areas `andhence bur-n more slowly.

Adjustment in the rate at which this underiire a-ir flows upwardly through the burning bagasse bed from windbox 32 may be made in any suitable manner, as desired to satisfy combustion requirements. Shown for this purpose is damper 33 at the windbox entrance manipulated through control 77 at the furnace front. In this way the fuel-air ratio is accurately adjustable to the value which results in the maximum efficiency lof bagasse combustion.

If desired, the underflre air'just described may be supplemented by overre air such as can be introduced by jets 44 into the combustion chamber above the level 'of spreader-Stoker 46. In an installation 4such as shown, those overfire jets are optional since major burning requirements are satisfactorily supplied by the underre all'.

High rates of heat release are readily attainable from the bagasse when burned by the new technique here described, and widely varying load requirements on the boiler furnace can easily be met. Excellent performance of the disclosed furnace is realized at rates of from 400,000 to 1,000,000 B. t. u. per hour per square foot of grate area; and satisfactory functioning at heat release rates both below and above that range also may be obtained. Lower limit is set by a generation of heat sutilcient for proper drying of the incoming bagasse before it reaches the grate; upper limit must not produce a rise of combustion gases from the grate rapid enough to carry over unburned bagasse particles into the boiler passes in objectionable quantity. As indicated above, the spreadv 'boiler furnace. Assuming that the disclosed combustiony chamber has 144 square feet of grate surface 21 and that the lStoker-injected bagasse has a heating value of 4000 B. t. u. per p-ound and weighs six pounds per cubic foot as taken from the grinding mill, there may at the 1,000,000 B. t. u. per square foot per hour heat release rate be burned on that illustrated nine-by-*sixteen foot grate area during each hour of furnace operation some 38,000 pounds (19 tons) of the bagasse which occupies 6333 cubic feet as introduced into the furnace. If allowed to pile up on the 144 square foot 4grate the bagasse supplied to the grate surface at this rate would in one hour build into a column about 44 feet high. This is nearly two and one half times the eighteen foot spacing between combustion chamber grate 21 and roof 16; it represents a build up rate of one foot every 1.36 minutes; yet so effective is the new combustion technique that the thickness of the burning bagasse bed never goes beyond two lor three inches during lfurnace operation.

Ifintrod-uced into the same furnace at a rate suthcient to liberate 1,000,000 B. t. u. of heat per square foot of grate each hour, crushed coal weighing 50 pou-nds per cubic foot and having a heating valve of 14,000 B. t. u. per pound would in `one hour build a corresponding column of only 1.44 feet (10,400 pounds and 208 cubic feet) on the grate. This is only 3.28 percent yof the 44 foot column of bagasse. Hence, to liberate heat at a given rate bagasse must be spread into a furnace with far greater rapidity than is coal, the ratio for the examples stated 'being 3.5 to 1 by weight and about 30 to 1 by volume. Prior to the present invention an accomplishment of such accelerated spreading accompanied by successful 4burning of the bagasse was not pos-sible.

The improved bagasse burning technique here described leaves only a minimum of ash residue on the grate 21 or 22. The dump-type grate 21 of Fig. 1 arranged in two or more side-by-side sections as shown at A-B--C etc. in Fig. 2 may satisfactorily have such accumulated ash cleaned therefrom once during each eight vhour operating shift (or even less frequently); preferably the individual sections are so cleaned one after another in shortly-spaced sequence in a way which keeps the boiler continuously on the line without objectionable reduction in output.

Procedure for each section is first to close (by way of control 77) the air inlet damper 33 for the section, then to tilt (by way of control 78) the grate bars 2i endwise to allow the ash to fall between tilted bar rows linto the pit space 32 therebelow, thereupon to return the grate bars 21 to the operating position of Figs. l and 6, and thereafter to reopen the air inlet damper 33. The arrangement illustratively shown contemplates that the ash thus released into pit 32 then be removed therefrom (preferably while damper 33 is still closed) by opening door 80 and employing a long handled scraper or scoop to pull the ash onto the oor at the furnace front (for later hauling away as by a wheelbarrow). Other removal expedients are of course employable.

The named ash dumping from each section of the grate 21 into the pit therebeneath requires less than one minute (usually about 30 seconds). During that short interval the introduction of bagasse over the section by spreaderstoker 46 can either be shut off or continued without interruption. in either event, a new accumulation of bagasse upon the cleaned section surface (following ash dumping) automatically reignites itself from the heat stored in the fuel bed on an adjacent section aided by the flame sweeping thereover. The furnace fire therefore need never be lost during the sequential grate section cleaning here described.

While the ash thus dumped from each section of the grate 21 is being taken from the pit 32 therebeneath (with section damper 33 closed and section door Sti opened), the fire on this section thereabove burns by natural draft until door 80 is again closed and damper 33 is again opened, when normal combustion is restored. With a four-section grate the attendant temporary reduction in section heat release has little effect on steam output, the remaining three active sections (particularly when under automatic control) then lserving to carry the boiler' load. Consequently, sequential dumping of the several grate sections one after another assures continuous boiler output during the entire grate-cleaning period.

When the grate is of the continuous discharge traveling type shown at 22 in Fig. la, the ash removal is progressive and is then automatically effective without even temporary interruption in a burning of the bagasse on and above the grate surface. High burning efficiency may therefore be achieved with both of the grate types here illustrated.

Such y ash and cinders as are carried from the combustion chamber into the boiler passes may satisfactorily there be collected in one or more bottom hoppers installed as at points 41 4?. of Fig. 1, returned to the combustion chamber at some suitable point such as 43 by con- Vventional pressure jet means diagrammatically indicated in Fig. 1, and thereupon reburned for useful reclamation of the combustible content. In practice the quantity of this cinder carry-over is found to be small (not more than one or two percent of the total fuel tired). This continuous return of the carryover material deposited in the boiler pass hoppers contributes to the uninterrupted boiler operation earlier described.

Salient advantages of the new technique from d to v70%. Heat formerly lost from the separate l2 oven is now initially liberated in the main boiler setting where useful conversion into steam takes place; moreover, the new spreader tiring allows superior control of fuel-air ratio and thereby further raises burning efficiency. This reduces bagasse consumption and makes auxiliary oil firing (as at burner 36) less necessary.

Boiler capacity is better utilized. The new furnacestoker-feeder organization lends itself to automatic control (as via feeder speed adjuster 67 and underre air damper 33) of steam output and pressure, thereby regulating fuel consumption in accordance with boiler load demand. This assures better performance both of the boiler and of the steam utilizing equipment supplied therefrom.

Furnace availability is vastly improved. A Dutchoven type furnace must be taken off the line daily (at least) for cleaning accumulated ash from the oven hearth and weekly to remove carry over from the back connections of the boiler. Each such cleaning may occasion substantially complete shut down. The new Stoker-fired boiler can be kept on the line continuously throughout the entire grinding season (of several months); the main ash being removable from the grate sections without dropping boiler output and the carryover material being continuously returned to the combustion chamber.

Cleaning of res is easier and quicker. The new Stoker-tired furnace with two to four sections of dump grate can be freed of ashes in ten to fifteen minutes with little or no loss in output of boiler steam. Prior art Dutch oven furnaces may take as much as thirty minutes to clean, with almost complete loss in boiler output during this time.

Boiler and furnace maintenance is reduced. New Stoker firing avoids periodic inrush of cold air that accompanies cleaning of Dutch-oven furnaces, and thereby greatly cuts down expansion stresses and minimizes spalling of brickwork. This prolongs the apparatus life while lowering expense for repairs.

Compactness is increased and ioor space is reduced. Fitting of the spreader stoker under the boiler eliminates requirement for Dutch oven external to the main setting. This almost halves the front-to-rear overall dimension, conserves floor space, and lowers initial cost of the boiler furnace installation.

Starting of fire is easier. Readily accomplished by use of oily waste or other -small kindling near furnace front from which fire spreads over entire grate surface when bagasse feed and forced draft are started. There is no need to first heat up combustion chamber walls and roof with wood or fuel oil, as must be done in starting a Dutch-oven furnace.

Fly ash emission is minimized. New stoker firing of bagasse with combustion control and cinder recovery cuts stack emission to a minimum. Dutch oven type furnaces are very troublesome in this respect.

Application to incineration burning ln addition to the generation of steam as here disclosed, the new bagasse-burning technique of this invention may with advantage also be employed for an incineration burning of bagasse in situations where mere disposal is the only objective and where it may not be desirable to apply the liberated heat to any useful purpose.

In such instances the furnace apparatus of Fig. l may be modified by: (a) removal of all boiler pressure parts (boilerV tubes 10, drums 11-12 and water wall tubes 12); and (b) redesign of the combustion chamber above grate 21 to lead directly into a draft-inducing stack (not shown) and to provide for an air cooling of its Walls in a manner well known to the incineration art. Modification along these general lines renders the furnace apparatus of Fig. 1 suitable for an incineration burning of excess bagasse without useful reclamation of the liberated heat.

Such burning proceeds in substantially the same manner aromas as in the steam-generating furnace here shown (Fig.'1 and later views). Since full rdescription thereof has already been given, `it will suffice to say that an incineration burning of the bagasse on g'rate 21 (or 22) at the combustion chamber bottom is characterized by the same superior convenience, high efciency, accuracy of control and fastness of progression that the spreader stoker 46 and uniquely coordinated feeder 48 makes possible when the furnace forms part of a steam generating boiler.

Many of the practical advantages listed for the steamgenerating application are therefore pertinent to this incineration use of the new bagasse burning technique. These include compactness of apparatus, convenience of introducing the bagasse into the combustion chamber, low furnace maintenance, easy starting of lire, convenience of ash removal, accurate and flexible control of the bagasse feed rate, widely adjustable lrapidity with which the bagasse may be burned, and uninterrupted availability of the furnace.

Summary Although the new combustion technique vhere disclosed is particularly useful for the burning of bagasse fuel derived from sugar cane stalks as crushed in a syrup extracting mill, it will be apparent that the same technique can with comparable practical benefit also be enrployed in the burning of other cellulose-base fuels whose characteristics are sufficiently similar to those of bagasse to permit the special feeder 48 satisfactorily to dispense same, the spreader stoker 46 properly to spread same over the combustion chamber grate 21 or 22, and the furnace which includes that grate satisfactorily to burn same by the aid of controlled underre air. Examples of fuelsy possessing such equivalency include Wood yShavings, `finely comminuted chips and bark (hogged fuel), as well as certain other cellulose-base materials in .comminuted form that have sufficient heating value to maintain combustion in conjunction with the moisture that they contain.

From the foregoing it will accordingly be seen that this invention has provided a vtechnique for burning bagasse-type fuels more conveniently and more eiciently than has been possible heretofore; that it has enabled such burning to proceed continuously without the prior necessity of periodic furnace shut down; that it has simplitied the construction, lowered the cost and improved the performance of furnace apparatus wherein cellulose fuels of the bagasse type can effectively be burned; that it has accomplished satisfactory burning of bagasse-type fuels on furnace grates (both stationary and traveling) when spreader stokers are used to feed the fuel to those grates; that it has enabled the so used spreader stoker to distribute the bagasse fuel over the grate surface with such controlled uniformity that even and complete burning will be assured and that fire blanketing will not occur (as in spots or otherwise) anywhere on the grate; that it has provided improved feeder apparatus capable of supplying the bagasse-type fuel to the spreader stoker impeller at a closely controlled uniform rate which may be accurately adjusted through a wide range of fuel-feed speeds; and that it has coordinated the several elements of the complete furnace-stoker-feeder system in a way uniquely matched with the special characteristics and burning requirements of bagasse-type fuels.

The inventive improvements are therefore extensive in their adaption and hence are not to be restricted to the specific form here disclosed by way of illustration.

What we claim is:

l. In apparatus for feeding bagasse derived from sugar cane stalks as crushed in a syrup-extracting mill which crushing converts the stalk material into a tangled mass of closely intermingled fibres that resist separation, the combination of a feed hopper adapted to be charged at the top with bulk bagasse, the hopper being vertically Yextended to define an upright column of the bulk bagasse and having at one side thereof an upright wall provided at the bottom thereof with a downwardly presented cutter edge; a rotary feed drum mounted on a generally horizontal axis .and having a drum surface spaced below the cutter edge and located with relation to the cutter edge sov that the cutter edge overlies the mid region of the top of the drum, the drum being of diameter suicient to extend from the vertical plane of said cutter edge substantially to the opposite side of the hopper and thus underlie substantially the entire horizontal section of the hopper, and the drum having a plurality of blades extended generally axially thereof and projecting radially from the drum surface to pass beneath said cutter edge in spaced relation thereto, the blades being spaced from each other around the drum to form bagasse receiving pockets above the drum surface and below the cutter edge and said blades having serrated edges capable of biting into bulk bagasse in said feed hopper overlying the drum; means for rotating the drum in the direction in which the serrated blades and the intervening pockets pass under the column of bagasse in the hopper from the hopper wall opposite the cutter edge toward said cutter edge and then under and beyond the cutter edge and the thickness of the serrated blades being small in relation to the inter-blade spacing, whereby said serrated blades on the drum lirst bite into the bulk bagasse in the hopper and then cooperate with said cutter edge to sever mat-like portions of bagasse from the column of said bulk bagasse and whereby the pockets carry such severed portions under and beyond the cutter edge; and discharge passage means for receiving the severed portions of vbagasse from the pockets of the feed drum and for delivering said portions of bagasse to a desired point.

2. In vapparatus for feeding bagasse derived from sugar cane stalks as crushed in a syrup-extracting mill which crushing converts the stalk material into a tangled mass of closely intermingled fibres that resist separation, the combination of a hopper adapted to be charged with bulk bagasse, the hopper being vertically extended to define an upright column of the bulk bagasse, a feed drum mounted below the hopper on a generally horizontal axis, the hopper having a generally upright side wall the lower margin of which extends lengthwise of the drum in spaced relation over the high or mid region thereof, the diameter of the drum being sufficient to extend from a point below the lower margin of said hopper wall substantially to the opposite side of the hopper, the drum having a plurality of circumferentially spaced blades extended generally axially thereof and projecting radially from the drum surface and providing a plurality of pockets at the drum surface intervening between the blades, means for rotating the drum in the direction in which the blades travel under the column of bagasse in the hopper from the side of the hopper opposite to said hopper wall across and upwardly of the hopper to the region of said wall and thence under the wall and downwardly in the region beyond said wall, a casing structure adjoining said hopper wall and peripherally enclosing the drum in said region beyond the hopper wall, the casing structure providing a substantially unobstructed arcuate chamber accommodating the drum blades and intervening pockets and having a peripheral bagasse discharge outlet adjacent a lower portion of the drum, the drum blades being spaced relatively widely as compared with the blade thickness to provide for filling the intervening pockets with bulk bagasse by the weight of the superimposed column theerof and said blades having serrated edges capable of biting into the bulk bagasse at the lower end of the column, and said upright hopper wall having a downwardly presented cutter edge along its lower margin between the hopper space and `the'clamber in the adjoining casing structure, said cutter edge being in closely spaced relation to the outer serrated edges of the drum blades during rotation of the drum and cooperating with the drum blades to sever from the bulk bagasse in the hopper mat-like portions of bagasse in said pockets and thereby provide for delivery of the severed portions within the casing structure to said discharge outlet.

3. The bagasse feeding apparatus of Yclaim 2 wherein said downwardly presented cutter edge is adjustable in its spacing from the serrated edges of the drum-carried blades that pass beneath the cutter edge during operation of the apparatus.

4. In apparatus for feeding bagasse derived from sugar cane stalks as crushed in a syrup-extracting mill which crushing converts the stalk material into a tangled mass of closely intermingled fibres that resist separation, the combination of a feed hopper adapted to be charged at the top with bulk bagasse, the hopper being vertically extended to define an upright column of the bulk bagasse and having at one side thereof an upright wall provided at the bottom thereof with a downwardly presented cutter edge; a feeder mechanism below the hopper comprising a carrier having an endless movable carrier surface underlying substantially the entire horizontal section of the hopper and extended under and beyond the upright plane of said cutter edge, said carrier surface being downwardly spaced from the cutter edge and having a plurality of blades extended generally transverse the direction of movement thereof and projecting therefrom to pass beneath said cutter edge in spaced relation thereto, the blades being spaced from each other in the direction of movement of the carrier surface to form bagasse receiving pockets above the carrier surface and below the cutter edge and said blades having serrated edges capable of biting into bulk bagasse in said feed hopper overlying the carrier surface; means for driving the carrier in the direction in which the serrated blades and the intervening pockets pass under said column of bagasse in the hopper from the hopper wall opposite to the cutter edge toward saidcutter edge and then under and beyond the cutter edge and the thickness of the serrated blades being small in relation to the interblade spacing, whereby said serrated carrier blades first bite into the bulk bagasse in the hopper and then cooperate with said cutter edge to sever mat-like portions of bagasse from the column of said bulk bagasse and whereby the pockets carry such severed portions under and beyond the cutter edge; and discharge passage means for receiving the severed portions of bagasse from the pockets of the feeder mechanism and for delivering said portions of bagasse to a desired point.

5. The bagasse feeding apparatus of claim 4 wherein said movable carrier surface is in the form of an endless belt.

6. The bagasse feeding apparatus of claim 4 wherein said discharge passage means are in the form of a generally upright feed chute having its upper end positioned to receive the severed portions of bagasse from the pockets'between serrated blades and having its lower end positioned to deliver said portions of bagasse to a desired point under the action of gravity.

7. The bagasse feeding apparatus of claim 4 wherein charging of the bulk bagasse into the top of said feed hopper is accomplished by means of a conveyor, said conveyor beingarranged to bring bulk bagasse to the hopper at least as fast as severed portions of this bagasse are fed into said discharge passage by the serrated blades of the apparatus whereby the hopper is kept fully filled by the conveyor.

References Cited in the le of this patent UNITED STATES PATENTS 536,047 Schmack Mar. 19, 1895 767,083 Reagan et al. Aug. 9, 1904 951,499 Duncan Mar. 8, 1910 1,143,634 Lane et al June 22, 1915 1,319,377 Cooper Oct. 21, 1919 1,505,723 Mueller Aug. 19, 1924 1,538,450 Stewart May 19, 1925 1,619,550 Thebaud et al. Mar. 1, 1927 1,977,644 Paxton Oct. 23, 1934 2,034,876 Morgan Mar. 24, 1936 2,337,945 Stripe Dec. 28, 1943 2,532,584 Vagim Dec. 5, 1950 2,558,799 Thomas July 3, 1951 2,579,326 Lang Dec. 18, 1951 v 2,736,461 Dueringer et al Feb. 28, 1956 

1. IN APPARATUS FOR FEEDING BAGASSE DERIVED FROM SUGAR CANE STALKS AS CRUSHED IN A SYRUP-EXTRACTING MILL WHICH CRUSHING CONVERTS THE STALK MATERIAL INTO A TANGLED MASS OF CLOSELY INTERMINGLED FIBRES THAT RESIST SEPARATION, THE COMBINATION OF A FEED HOPPER ADAPTED TO BED CHARGED AT THE TOP WITH BULK BAGASSE, THE HOPPER BEING VERTICALLY EXTENDED TO DEFINE AN UPRIGHT COLUMN OF THE BULK BAGASSE AND HAVING AT ONE SIDE THEREOF AN UPRIGHT WALL PROVIDED AT THE BOTTOM THEREOF WITH A DOWNARDLY PRESENTED CUTTER EDGE; A ROTARY FEED DRUM MOUNTED ON A GENERALLY HORIZONTAL AXIS AND HAVING A DRUM SURFACE SPACED BELOW THE CUTTER EDGE AND LOCATED WITH RELATION TO THE CUTTER EDGE SO THAT THE CUTTER EDGE OVERLIES THE MID REGION OF THE TOP OF THE DRUM, THE DRUM BEING OF DIAMETER SUFFICIENT TO EXTEND FROM THE VERTICAL PLANE OF SAID CUTTER THUS UNDERLIE SUBSTANTIALLY THE ENTIRE HORIZONTAL SECTION OF THE HOPPER, AND THE DRUM HAVING A PLURALITY OF BLADES EXTENDED GENERALLY AXIALLY THEREOF AND PROJECTING RADIALLY FROM TEH DRUM SURFACE TO PASS BENEATH SAID CUTTER EDGE IN SPACED RELATION THERETO, THE BLADES BEING SPACED FROM EACH OTHER AROUND THE DRUM TO FORM BAGASSE RECEIVING POCKETS ABOVE THE DRUM SURFACE AND BELOW THE CUTTER EDGE AND SAID BLADES HAVING SERRATED EDGES CAPABLE OF BITING INTO BULK BAGASSE IN SAID FEED HOPPER OVERLYING THE DRUM; MEANS FOR ROTATING THE DRUM IN THE DIRECTION IN WHICH THE SERRATED BLADES AND THE INTERVENING POCKETS PASS UNDER THE COLUMN OF BAGASSE IN THE HOPPER FROM THE HIPPER WALL OPPOSITE THE CUTTER EDGE TOWARD SAID CUTTER EDGE AND THEN UNDER AND BEYOND THE CUTTER EDGE AND THE THICKNESS OF THE SERRATED BLADES BEING SMALL IN RELATION TO THE INTER-BLADE SPACING, WHEREBY SAID SERRATED BLADES ON THE DRUM FIRST BITE INTO THE BULK BAGASSE IN THE HOPPER AND THEN COOPERATE WITH SAID CUTTER EDGE TO SEVER MAT-LIKE PORTIONS OF BAGASSE FROM THE COLUMN OF SAID BULK BAGASSE AND WHEREBY THE POCKETS CARRY SUCH SEVERED PORTIONS UNDER AND BEYOND THE CUTTER EDGE; AND DISCHARGE PASSAGE MEANS FOR RECEIVING THE SEVERED PORTIONS OF BAGASSE FROM THE POCKETS OF THE FEED DRUM AND FOR DELIVERING SAID PORTIONS OF BAGGASE TO A DESIRED POINT. 